Grantee Research Project Results
Final Report: Efficient Acid Mine Drainage Multimetal Removal/Recovery
EPA Contract Number: EPD04022Title: Efficient Acid Mine Drainage Multimetal Removal/Recovery
Investigators: Buschmann, Wayne E.
Small Business: Eltron Research & Development Inc.
EPA Contact: Richards, April
Phase: I
Project Period: March 1, 2004 through August 31, 2004
Project Amount: $69,996
RFA: Small Business Innovation Research (SBIR) - Phase I (2004) RFA Text | Recipients Lists
Research Category: SBIR - Mining , Hazardous Waste/Remediation , Small Business Innovation Research (SBIR)
Description:
This research project is directed towards the development of an automated, solar-powered, flow-through prototype system for the continuous unattended treatment of acid mine drainage (AMD), which can be found at thousands of abandoned mines. During Phase I, Eltron Research, Inc., fabricated a novel advanced electrolytic technology for efficient aqueous source metal contaminant removal/recovery and incorporated it into a pilot-scale prototype automated water treatment system where it was tested for multiple metal removal capabilities from dilute (< 300 mg/L) aqueous waste streams. The technology is centered around a novel electrolytic cell design based on an established spouted bed technology. The technology recently demonstrated significant promise towards treating dilute waste streams of multiple metals, such as those resulting from AMD or those found at numerous contaminated U.S. Department of Energy (DOE) sites. Improved removal efficiencies at lower contaminant concentrations, dramatically reduced fluid management power costs, and higher operating current densities allowing smaller and cheaper modular treatment units will result from the proposed cell design. The technology will be compact, reagentless, and require no feedstream pretreatment; it also will recover the contaminant as a compact, concentrated, solid, and potentially pure saleable product. Cell performance, stability, and design optimization were explored with the common model AMD contaminants of copper and zinc. Evaluations were expanded to include nickel and the very challenging target, manganese. The results obtained were used to develop treatment cost estimates, design a prototype pilot-scale remediation system for Phase II implementation and subsequent field trial evaluation, and perform feasibility analyses against various AMD scenarios.
Summary/Accomplishments (Outputs/Outcomes):
During Phase I, a new mechanical cathode spouting mechanism was designed and fabricated along with a new electrolytic cell design to accommodate the mechanism. This electrolytic cell was incorporated onto a prototype solar-powered system platform for testing. Metal removal performance was evaluated for copper (positive reduction potential), nickel, zinc (negative reduction potentials), and manganese (reduction potential more negative than water). Starting concentrations of metals were nominally 200-900 mg/L in sulfuric acid solution to simulate AMD. The performance results were used to conduct a technical and market feasibility analysis and to design a prototype pilot-scale system suitable for field testing.
A mechanically robust and reliable mechanical cathode spouting mechanism was assembled and used throughout Phase I without any problems. A new electrolytic cell design also was fabricated that was simple in design and provided reliable, leak-free performance. The new mechanical drive configuration allowed fluid ports to be repositioned, providing a system that potentially can be automated to drain reclaimed metals/solids and be refilled with fresh cathode substrate. Several methods for preparing inexpensive cathode substrate material were determined. The new electrolytic cell was installed onto a prototype solar-powered system platform where it was operated for performance testing.
The new AMD treatment system was very effective for removing/reclaiming copper (and presumably other metals with positive reduction potentials) from dilute aqueous streams. Initial results demonstrated treatment power costs of $0.435/1,000 gallons, with these power costs eliminated by the solar-powered system. Treated water was discharged, with typical residual copper concentrations of 90-400 μg/L (ppb), and acid pH was neutralized. The AMD treatment system also demonstrated modest removal of nickel and zinc at low concentrations, a very difficult goal. Operating conditions determined removal efficiencies for the above metals, making improvements in removal efficiencies possible and demonstrating selectivity of metal removal. Removal of manganese was poor, but initial results suggest that further examination is justified. Optimizing removal of metals with negative reduction potentials was found to be a balance between pH, feed flow rate, and diffusion kinetics that determines the balance of competing metal reduction and corrosion processes in acid media.
Development of a small-scale AMD treatment system capable of 6 gpm in Phase II is feasible with only an eight times scale-up factor over the Phase I system. Production of a custom prototype system for small-scale field testing was estimated at less than $30,000. The resulting technology will provide a combination of the desired treatment system features with an acceptable capital cost for end-users in the mining and environmental remediation industries that are not available with current methods or technologies.
Conclusions:
The results of Phase I suggest that nearly complete AMD treatment can be achieved economically in a single process, in remote locations, with virtually no consumables, and provide relatively pure (solid) metals as a saleable or reusable product. The new AMD treatment system will be applicable to treatment of acid mine and acid rock drainage, remediation of contaminated DOE sites, and treatment of other heavy metal containing waste streams from industrial discharge, including the semiconductor, electronics, and metal plating industries.
Supplemental Keywords:
acid mine drainage treatment, AMD, environmental remediation, heavy metal reclamation, solar powered system, remote site treatment, copper, zinc, nickel, manganese, mining, SBIR,, RFA, Scientific Discipline, INTERNATIONAL COOPERATION, Waste, POLLUTANTS/TOXICS, Sustainable Industry/Business, Environmental Chemistry, cleaner production/pollution prevention, Chemistry, Chemicals, Hazardous Waste, New/Innovative technologies, Engineering, Environmental Engineering, Hazardous, hazardous waste treatment, detoxification, advanced treatment technologies, recovery, acid mine drainage, metal recovery , metal recovery, remediation, innovative technology, electrolytic technology, electrolytic reduction, innovative technologies, heavy metalsThe perspectives, information and conclusions conveyed in research project abstracts, progress reports, final reports, journal abstracts and journal publications convey the viewpoints of the principal investigator and may not represent the views and policies of ORD and EPA. Conclusions drawn by the principal investigators have not been reviewed by the Agency.